linux-kernel - Re: [PATCH RFC v1 1/2] rcu/tree: Add basic support for kfree

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 8 Aug 2019 15:37:00 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     Byungchul Park <byungchul.park@....com>,
        linux-kernel@...r.kernel.org, Rao Shoaib <rao.shoaib@...cle.com>,
        max.byungchul.park@...il.com, kernel-team@...roid.com,
        kernel-team@....com, Davidlohr Bueso <dave@...olabs.net>,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        rcu@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH RFC v1 1/2] rcu/tree: Add basic support for kfree_rcu
 batching

On Thu, Aug 08, 2019 at 06:34:15PM -0400, Joel Fernandes wrote:
> On Thu, Aug 08, 2019 at 01:51:29PM -0700, Paul E. McKenney wrote:
> [snip]
> > > Also, I am thinking that whenever we do per-slab optimization, then the
> > > kmem_cache_free_bulk() can be optimized further. If all pointers are on the
> > > same slab, then we can just do virt_to_cache on the first pointer and avoid
> > > repeated virt_to_cache() calls. That might also give a benefit -- but I could
> > > be missing something.
> > 
> > A sort might be required to make that work nicely, which would add some
> > overhead.  Probably not that much, though, the increased locality would
> > have a fighting chance of overcoming the sort's overhead.
> > 
> > > Right now kmem_cache_free_bulk() just looks like a kmem_cache_free() in a
> > > loop except the small benefit of not disabling/enabling IRQs across each
> > > __cache_free, and the reduced cache miss benefit of using the array.
> > 
> > C'mon!  Show some respect for the awesome power of temporal locality!!!  ;-)
> 
> Good point. I will try to respect it more in the future ;-) After all, it is
> quite a useful concept.

;-) ;-) ;-)

It still has to prove itself in real benchmarks, of course!

							Thanx, Paul